Method and apparatus for charging a thermostatic system

ABSTRACT

A method and apparatus for charging a thermostatic system with a condensable fluid. Essential parts of the apparatus are a storage container for the condensable fluid, a metering container and a charging head. The condensable fluid in the storage container exerts a vapor pressure and, with the use of valve means, vaporized fluid is caused to flow to the metering container until a first predetermined pressure is reached. With the use of other valve means vaporized fluid in the metering container is caused to flow through the charging head to the thermostatic system to be charged until a second lower predetermined pressure is reached. A reducing valve is between the storage container and the metering container to effect a superheated condition for the fluid flowing to the metering container.

llmte States Patent [151 3,636,992 Weidner 51 Jan, 25, 1972 [54] METHODAND APPARATUS FOR 2,846,118 8/1958 Matejka ..222/3 2,475,317 7/1949 Gess..141/7 (:HARGING A THERMOSTATIC 2,684,805 7/1954 McBean.. ..141/9 XSYSTEM Inventor: Eric Weidner, Augustenborg, Denmark lDanfoss A/S,Norclborg, Denmark May 11, 1970 Assignee:

Filed:

Appl. No.:

Foreign Application Priority Data References Cited UNITED STATES PATENTS10/1950 Kagi et a1. 222/57 X Primary ExaminerEdward J EarlsAttorney-Wayne B. Easton [5 7] ABSTRACT A method and apparatus forcharging a thermostatic system with a condensable fluid. Essential partsof the apparatus are a storage container for the condensable fluid, ametering container and a charging head. The condensable fluid in thestorage container exerts a vapor pressure and, with the use of valvemeans, vaporized fluid is caused to flow to the metering container untila first predetermined pressure is reached. With the use of other valvemeans vaporized fluid in the metering container is caused to flowthrough the charging head to the thermostatic system to be charged untila second lower predetermined pressure is reached. A reducing valve isbetween the storage container and the metering container to effect asuperheated condition for the fluid flowing to the metering container.

5 Claims, 1 Drawing Figure METHOD AND APPARATUS FOR CHARGING ATHERMOSTATIC SYSTEM The invention relates to a method of charging athermostatic system with a predetermined quantity of a noncondensiblemedium derived from a storage container, and particularly systems forrelief valve jets; the invention also relates to charging apparatus forperforming this method.

It is known practice to charge thermostatic systems which consist forexample of a temperature sensor and a working element connected thereto,through a capillary tube, with a condensable medium. The condensablemedia include sulphur dioxide and halogenized hydrocarbons such asmethyl chloride or the substances marketed under the trade names Freonor Frigen. In the working range they form a liquid-vapor charge, thevapor pressure of which is dependent upon tem perature.

The usual charging methods do not however enable very small quantitiesof a condensable medium to be charged into a thermostatic system in aprecise manner. Pressure-limited thermostatic systems for examplecontain, at the lowest working temperature, only a few drops ofcondensate, which must be completely evaporated just above thetemperature working range in order not to subject the system toexcessive pressure loading when a further rise in temperature takesplace. if the amount of the charge is only slightly smaller, the workingrange is limited, and if the amount of the charge is only slightlygreater, undesirable pressure loading occurs. A typical example of arelief valve jet of this kind is an expansion valve for refrigeratingplant, the sensor of which is subjected to tropical temperatures duringtransport.

The object of the invention is to provide a method of charging with thehelp of which it is possible to supply a thermostatic system withcondensable medium in a precise manner even when the quanitity of themedium is extremely small.

According to the invention this object is achieved by passing the mediumin the superheated condition to a measuring container until apredeten'nined first pressure obtains in this container, and by thenreleasing the medium from the container into the thermostatic systemuntil a predetermined lower second pressure obtains in the measuringcontainer.

Since the measuring container has a definite volume, the predeterminedchange in pressure corresponds to a precisely defined quantity ofcondensable medium. The method can be repeated to give the same resultsand indicates accurately what quantity of the medium is removed from themeasuring container on each occasion.

The superheated medium can only flow into the thermostatic systembecause of the difference between the pressure in the measuringcontainer and the pressure or partial pressure in the thermostaticsystem. A particularly rapid mode of operation results if at least partof the thermostatic system is so cooled during the charging operationthat the medium condenses in that part.

It is also expedient for the medium to be stored under pressure in theliquid condition in the storage container and for the pressure to berelaxed prior to entry of the medium into the measuring container. Afterthe pressure has been relaxed, the medium is available in a sufficientlysuperheated condition to enable the metering operation to proceed in amethodical manner. The measuring container can be kept at roomtemperature, and therefore does not need to be heated.

According to the invention, charging apparatus for performing the methodis characterized in that a measuring container having an inlet valve, anoutlet valve and a pressure gauge is disposed in the line extendingbetween the storage container and a charging head for connecting thethermostatic system. Depending upon the indication given by the pressuregauge, the inlet valve for filling the measuring container can then beopened and closed, and the outlet valve can be opened and closed forfeeding the medium.

This procedure can even be rendered automatic if the pressure gaugeactuates contacts which close the inlet valve at the predetermined firstpressure, and if required, open the outlet valve, and close the outletvalve at the predetermined second pressure and, if required, open theinlet valve. Charging can be carried out for example on an assembly lineusing a phased method, wherein the time required for filling themeasuring container is used each time for replacing the chargedthermostatic system by an empty one.

A reducing valve is expediently fitted between the storage container andthe inlet valve. This reducing valve provides the reduction of pressurerequired for superheating. Furthermore, it is advantageous for the pipeto run from the vapor compartment of the storage container, so that thereducing valve has only to handle vapor.

A very broad meaning is applied to the expression pressure gauge. It canconsist for example of two separate pressostats, one of which controlsthe inlet valve and the other the outlet valve. If the reducing valve isable to keep the pressure on the outlet side constant, this valve takesover part of the function of the pressure gauge.

The method is also suitable for charging such thermostatic systemswhich, apart from the above-mentioned condensable medium, also containanother medium, e.g., a noncondensible medium.

The invention will now be explained in more detail by reference to anembodiment illustrated schematically in the drawing.

It will be assumed that it is required to charge a thermostatic system1, which comprises a sensor 2, a siphon diaphragm 3 on a valve 4, and acapillary tube 5. A further short capillary tube 6 is used as atemporary connection on the charging head 7. The charging head 7 isconnected through a pipe 8 to a storage container 9, which contains acondensable medium 10 in liquid form. The pipe 8 runs from the vaporcompartment 11 of this container, passes through a reducing valve l2and, between an inlet valve 13 and an outlet valve 14, incorporates ameasuring container 15, to which a pressure gauge 16 is connected. Thesensor 2 is accommodated in a cooling container 17 which keeps thesensor at a low temperature. It will be assumed that all parts of thesystem are held at room temperature, whereas the sensor is held at aconsiderably lower temperature by the cooling container 17.

To charge the system 1, first the valve 13 is opened, valve 14 beingclosed. Medium in vapor form then flows through the reducing valve 12,is reduced in pressure and gradually builds up a pressure in themeasuring container 15. If the pressure gauge 16 indicates a pressure ofp,, the valve 13 is closed by hand or automatically.

Since substantially all of the quantity of the medium drawn from thecontainer 15 is contained in the system 1 (very small traces of vapor inthat portion of the pipe between the measuring container 15 and thesystem 1 can be ignored), the charging port 6 can be removed from thecharging head 7 and sealed. This cycle can then be repeated with a freshsystem.

lclaim:

1. A method for charging a thermostatic system with a predeterminedquantity of a condensable medium comprising the steps of storing acondensable medium in a fluidtight storage container, placing the upperpart of said storage container in fluid communication with a meteringcontainer until a first predetermined pressure in said meteringcontainer is reached, maintaining said metering container at roomtemperature, placing said metering container in fluid communication witha fluid containing part of a thermostatic system until a second lowerpredetermined pressure is reached in said metering container.

2. A method according to claim 1 including the step of superheating saidmedium at a point between said storage container and said meteringcontainer.

3. A method according to claim ll including the step of cooling saidfluid containing part of said system.

d. Apparatus for charging a thermostatic system with a predeterminedquantity of a condensable medium comprising a storage container forstoring a quantity of a condensable medium, a metering container, acharging head, first conduit means between said storage container andsaid metering container, second conduit means between said meteringcontainer and said charging head, valve means in said first and secondconduit means, and pressure responsive means connected to said meteringcontainer for operating said valves. 5

5. Apparatus according to claim 4 including a reducing valve in saidfirst conduit means between said storage container and said valve meansin said first conduit means.

1. A method for charging a thermostatic system with a predeterminedquantity of a condensable medium comprising the steps of storing acondensable medium in a fluidtight storage container, placing the upperpart of said storage container in fluid communication with a meteringcontainer until a first predetermined pressure in said meteringcontainer is reached, maintaining said metering container at roomtemperature, placing said metering container in fluid communication witha fluid containing part of a thermostatic system until a second lowerpredetermined pressure is reached in said metering container.
 2. Amethod according to claim 1 including the step of superheating saidmedium at a point between said storage container and said meteringcontainer.
 3. A method according to claim 1 including the step ofcooling said fluid containing part of said system.
 4. Apparatus forcharging a thermostatic system with a predetermined quantity of acondensable medium comprising a storage container for storing a quantityof a condensable medium, a metering container, a charging head, firstconduit means between said storage container and said meteringcontainer, second conduit means between said metering container and saidcharging head, valve means in said first and second conduit means, andpressure responsive means connected to said metering container foroperating said valves.
 5. Apparatus according to claim 4 including areducing valve in said first conduit means between said storagecontainer and said valve means in said first conduit means.